Heat exchanger for boat propulsion unit



Nov. 4, 1969 J. Aus'rEN HEAT EXCHANGER FOR BOAT PROPULSION UNIT Filed sept. 25, 1967 l I w w! ff United States Patent O 3,476,070 HEAT EXCHANGER FOR BOAT PROPULSION UNIT U.S. Cl. 11S-.S 10 Claims ABSTRACT OF THE DISCLOSURE A boat propulsion unit and heat exchanger having a propeller surrounded by an annular jet casing and driven by an internal combustion engine through a drive gear arrangement. At least a portion of the axial length of the casing is provided with a double wall to constitute a heat exchanger fluid receiving chamber for cooling one of the operating uids of the internal combustion engine, for example the cooling uid. The forward portion of the casing and the double walls are constructed as a single casting along with supply and discharge pipes leading to the chamber. The double walls of the casing provide an annular rearwardly facing opening that is closed by an annular member forming the discharge end of the casing. The casing is mounted by a rotatable carrier through the interposition of a connecting pipe having an oil chamber for the drive gear, and supply and discharge conduits.

BACKGROUND OF THE INVENTION In known boat propulsion units, the internal combustion engine has been cooled directly by means of sea or fresh water, which is pumped to the internal combustion engine, circulated and discharged to the environment from where it came. It is also known to provide a cooling system with two heat exchange fluids; one of the fluids being in a closed engine cooling circuit and the other fluid being the environment fresh or seat water that is pumped in heat exchange relationship with the first fluid in the closed engine cooling circuit.

These known cooling systems suffer from the disadvantage that they are subjected to a high degree of corrosion when operating on sea water and become easily clogged when operating in fresh water. In addition, impurities are frequently drawn into the system that can cause considerable cooling difficulties, unless adequate filtering installations are provided.

SUMMARY OF THE INVENTION It is an object of the present invention to covercome the above-noted disadvantages of known boat propulsion unit cooling systems.

The present invention relates to a propulsion unit for boats or the like including a propeller adapted to be driven by an internal combustion engine through a propeller drive gear. The propeller is surrounded by an annular jet-casing formed with a double wall over at least a part of its length to deiine a heat exchanger for one of the operating fluids of the internal combustion engine,

The standard feed or circulating system of the internal combustion engine for the cooling water or the lubricating oil may be readily employed to circulate the respective operating uid (the cooling water or lubricating oil) through the jet-casing heat exchanger to produce a reliable cooling installation that is economical and not susceptible to corrosion or contamination. The operating fluid is in a closed circuit so that contamination and corrosion are not a problem for the operating uid. The environment fluid would normally pass through the jet-casing under the influence of the propeller so that there are no addi- 3,476,070 Patented Nov. 4, 1969 ice tional problems in regard to fouling and contamination with the environment uid. No additional pumps are required with the present invention when compared to a known system without a heat exchanger, because the normal operating fluid circulation pump is employed to move the operating fluid in heat exchange relationship and the propeller acts as a pump to move the environment fluid in heat exchange relationship. Also, no expensive filtering devices are employed, which is a considerable economic advantage over prior art constructions. Furthermore,l an anticorrosion and antifreeze agent may be added to the internal combustion engine cooling uid because it is in a closed circuit so that a self-servicing operation of the propulsion unit is achieved, even during long periods of inactivity.

The annular jet-casing preferably consists of a casing having a water inlet funnel merging into concentrically arranged outer and inner walls, and an annular member closing the rearward ends of the walls to form a hollow annular space therebetween for containing the closed circuit operating fluid. This construction provides a dimensionally stable hollow heat exchanger body which also forms a jet-casing rigidly attached to the boat for preventing the lboats propeller from becoming damaged by touching the bottom or other foreign objects. Preferably, the casing has separate supply and discharge conduits separated by an intermediate wall for supplying the heat exchanger chamber with the operating fluid, which may 4be the engine cooling water or engine lubricant, Thus a directional flow is provided through the jet-casing for eicient heat exchanger operation. Outstanding heat exchange values are obtained with construction of the casting and closure member from a highly heat conducting material, for example aluminum alloy or the like, and as an integral unit by bonding them together, for example by an adhesive.

Further objects, features and advantages of the present invention will become more clear from the following detailed description of a preferred embodiment with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a schematic illustration of a propulsion unit for motor boat having an internal combustion engine cooling system according to the present invention;

FIGURE 2 is an enlarged longitudinal partial crosssectional view through the jet casing and propeller mounting structure:

FIGURE 3 is a partial cross-sectional view through the connecting flange of the jet-casing taken along line 3-3 of FIGURE 2; and

FIGURE 4 is a cross-sectional view of the carrier taken in the direction of the arrow in FIGURE 2.

DETAILED DESCRIPTION OF THE DRAWING As shown in FIGURE l, the boat hull 1 contains therein an internal combustion engine 2 for rotatably driving the friction coupling or clutch 3, not shown in detail, which in turn drives the propeller drive arrangement 4. The propeller drive arrangement 4 includes a known Z-shaped drive train (indicated by the broken line in FIGURE l) for driving the boat propeller 6. The propeller 6 is mounted within and enclosed by a jet-casing '7. The jet-casing 7 is supported by a carrier 8, which is rotatably mounted with respect to the boat hull 1 in a head section 9 of the propeller drive arrangement 4.

As shown in FIGURE 2, the jet-casing 7 has an inlet water funnel 10 formed by a casting 11. The casting 11 has an intermediate portion with an outer wall 12 and a concentric inner wall 13. The rearward portions of the walls 12 and 13 are connected together by means of the annular wall member 14 to form a heat exchange chamber 15. The casting 11 includes the propeller boss 16, the brackets 17 for rigidly supporting the boss 16, and a connecting pipe 18 terminating in a flange 19. The closure member 14 is provided with an annular axial projection 20 that is inserted between and firmly bonded to the walls 12, 13 of the casting 11, with adhesive preferably being used. The casting 11 and the closure member 14 are constructed of a highly heat conducting material, preferably of aluminum alloy by the pressure casting process.

As shown in FIGURES 2-4, the operating fluid is supplied to and discharged from the heat exchanger chamber by means of a supply conduit 21 and a discharge conduit 22 that is separated by an intermediate wall 23 within the connecting pipe 18. The connecting pipe 18 is rigidly secured to the carrier 8 of the propeller drive arrangement 4 by means of its flange 19 and a corresponding flange on the carrier 8 with the interposition of a sealing gasket 24; bolts or the like may be used. It is preferable that the carrier 8 is also constructed by aluminum by pressure casting. The carrier 8 is provided with supply and discharged conduits 25 and 26 that are aligned with conduits 21 and 22, respectively, at one of their ends and aligned with corresponding passageways leading through the head section 9 into the boat hull at their other ends. As schematically shown in FIGURE l with broken lines, the conduits 25 and 26 are connected to the waterpump 27 and the water return hose or pipe 28 of the internal combustion engine 2 for cooling.

During operation of the boat, the water pump 27 circulates the engine cooling system water through the pipe 28 into the conduit 25, through the conduit 21, through the substantially annular heat exchanger chamber or conduit 15 of the jet-casing 7, through the conduit 22, through the conduit '26, and finally back to the pump 27. When the engine operating fluid, in this case the engine cooling water, passes through the heat exchanger chamber 15, it is cooled by the heat passing through the inner and outer walls 12 and 13 of the jet-casing 7 that are in heat exchange contact with the circulating cooler fresh or sea environment water; thus, the temperature of the engine cooling fluid is lowered.

In internal combustion engines with air-cooled working cylinders, the above-described heat exchanger installation may be used for cooling the engine lubricating oil without requiring any alteration except with respect to the engine hookups.

Although a preferred embodiment of the present invention has been described in detail with respect to an inboard motor boat, the basic principles may be employed with equal advantages in an outboard motor propulsion unit. The heat exchanger device of the present invention may be also used for cooling the fuel supply when the boat propulsion unit and fuel supply are arranged within a closed space having an undesirably high ambient temperature.

Although a preferred embodiment of the present invention has been described in detail, additional variations, modifications and embodiments are contemplated within the spirit and scope of the present invention as defined by the following claims.

I claim:

1. A propulsion unit for boats having a propeller to be mounted outboard of a boat hull driven through a propeller drive gear by a source of power to be positioned within the boat hull having at least one operating fluid, the improvement comprising: an annular jet casing on said propulsion unit and surrounding said propeller; and said casing having a double wall thickness defining a chamber at least over a part of its length and having inner and outer cooling surfaces forming an operating fluid passageway to constitute heat exchanger means for one of the operating uids of the source of power and an inlet and outlet means in communication with said chamber for the flow of one of the operating fluids.

2. A propulsion unit according to claim 1, wherein said casing consists of a casting having a forward water inlet funnel merging axially into intermediate outer and inner walls forming the double wall thickness, and a rearward annular member closing the rearward ends of said walls to form said passageway as a hollow substantially annular chamber.

3. The propulsion unit of claim 2, wherein said casting includes a connecting pipe having separate supply and discharge conduits, and intermediate wall means dividing said substantially annular chamber into a single conduit having two ends; said supply and discharge conduits being connected respectively to said conduit ends.

4. The propulsion unit according to claim 3, wherein said casting and said annular member are constructed of a highly heat conducting material, and rigidly bonded to each other.

5. The propulsion unit according to claim 4, including carrier means rotatably mounted with respect to the boat for supporting said jet-casing.

6. The propulsion unit according to claim 5, wherein said carrier means and said connecting pipe include aligned drive train receiving chambers containing lubricating oil, said carrier means including separate supply and discharge conduits aligned with said supply and discharge conduits of said connecting pipe respectively.

7. The propulsion unit according to claim 6, including an internal combustion engine having cooling liquid conduits connected with said supply and discharge conduits.

8. The propulsion unit according to claim 2, wherein said casting and said annular member are constructed of a highly heat conducting material, and rigidly bonded to each other.

9. The propulsion unit according to claim 1, including carrier means rotatably mounted with respect to the boat for supporting said jet-casing.

10. The propulsion unit according to claim 2, including carrier means rotatably mounted with respect to the boat for supporting said jet-casing.

References Cited UNITED STATES PATENTS 899,359 9/1908 Wadagaki 11S- 42 X 3,170,284 2/1965 Monnich 11S-42 X 3,179,081 4/1965 Backhaus et al. ll5 42 3,306,046 2/1967 Trabb 115--42 X ROBERT A. OLEARY, Primary Examiner THEOPHIL W. STREULE, Assistant Examiner U.S. Cl. X.R. 11S-42; 165-44 

